Origin of Ti-rich eclogite and ruffle deposit in the the southern Sulu UHP metamorphic belt, China.

Ti-rich eclogites in the southern Sulu ultrahigh-pressure (UHP) metamorphic belt may be divided into two types: Fe-and Ti-rich ilmenite eclogite and Ti-rich rutile eclogite. The Fe-Ti eclogites contain abundant ilmenite and Ti-magnetite with minor rutile and have very low SiO2 (38.0-42.3%), Na2O+K2O (0.48-2.13%), Zr, Nb, Ta, Ba, Rb and total REE contents but relatively high total FeO (18.24-25.33%), V and Co contents. Their REE patterns are characterized by more or less depletion of LREE and pronounced positive Eu anomalies. The Ti-rich rutile eclogites have abundant rutile and apatite and show a wide range of SiO2 (38.0-54.8%) and relatively low FeO and high P2O5 contents (up to 4.1%); moreover, their TiO2 contents are positively correlated with P2O5 contents. Primitive mantle-normalized trace element patterns of the rutile eclogites show negative anomalies of Rb, Th, K, Nb, Pr, Nd, Eu, Ti and Lu and positive anomalies of Ba, Sr and Zr. In addition, the rutile eclogites have relatively high REE contents and LREE-enriched and HREE-depleted patterns. The petrological and geochemical characteristics mentioned above indicate that the protoliths of Fe-Ti eclogites were Fe-Ti gabbros in a layered ultramafic to mafic intrusion formed by intensive fractional crystallization of basaltic magma.